The following background information may present examples of specific aspects of the prior art (e.g., without limitation, approaches, facts, or common wisdom) that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon.
The following is an example of a specific aspect in the prior art that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon. By way of educational background, another aspect of the prior art generally useful to be aware of is that industrial and consumer electronic devices are known to be powered by battery, direct current (DC), alternating current (AC) or combinations thereof. Whether battery, DC or AC powered the voltage of the power source must often be converted from one voltage to another voltage before it is delivered to an electronic element. An electronic element, in an electronic device, is conventionally referred to as a “load”. A load in an electronic device may be a CPU, a memory device, a hard disk, an ASIC (application specific integrated circuit), and so forth. Each load requires a specific voltage to operate. The apparatus that converts one voltage to another is typically called a “converter” or a “power converter”. A converter that raises one voltage to another voltage is typically called a “boost converter”, and a converter that reduces one voltage to another voltage is typically called a “buck converter”. A common type of converter used to convert one voltage to another voltage is a switching power converter (a switching power converter may also be referred to as a switching power supply or a switch mode power supply). Conventionally, a switching power converter will incorporate a switching regulator, and switching regulator circuit, when converting one voltage to another voltage.
The following is another example of a specific aspect in the prior art that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon. By way of educational background, another aspect of the prior art generally useful to be aware of is shown in FIG. 1. FIG. 1 illustrates a schematic of an exemplary prior art buck topology switching regulator circuit as may be used in a switching power converter. The buck switching regulator circuit is usually comprised of a switch 100, a diode 110 and a filter, which further may be comprised of an inductor 120 and a capacitor 130. Switch 100 may be a FET, MOSFET, BJT, IGBT or other suitable electronic switching device. During typical operation of the buck switching regulator circuit the switch 100 alternates its state between the on-state and the off-state. As a result, a square wave (FIG. 1) is generated on the switching node 140 of the buck switching regulator circuit. The square wave is then typically rectified by a rectifier or an LC filter (FIG. 1). The diode 110 allows the current to continue to flow through the inductor 120 while the switch 100 alternates between the on-state and the off-state. The output voltage Vo of the buck switching regulator circuit is a function of the duty cycle D (FIG. 1) of the switch 100. Typically, in a buck switching regulator circuit, the time averaged voltage (Vin*D) on the switching node 140 is the same as the output voltage Vo (Vo=Vin*D). The maximum voltage of the square wave is the same as the input voltage Vin because the switch is connected to the input voltage Vin.
The following is yet another example of a specific aspect in the prior art that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon. By way of educational background, another aspect of the prior art generally useful to be aware of is shown in FIG. 2. FIG. 2 illustrates a schematic of an exemplary prior art boost topology switching regulator circuit as may be used in a switching power converter. The boost switching regulator circuit is typically comprised of a switch 200, a diode 210, a filter 220 and a capacitor 230. Switch 200 may be a FET, MOSFET, BJT, IGBT or other suitable electronic switching device. The switch 200 is connected after the filter 220 and the output voltage Vo is rectified through the diode 210 when the switch 200 is in the off-state or when the diode 210 conducts. The output voltage Vo of the boost switching regulator circuit is a function of the duty cycle D (FIG. 2) of the switch 200. Since the filter 220 between the input voltage Vin and the switching node 240 rectifies the square wave into the output voltage Vo with no loss, the time averaged voltage on the switching node is the same as the input voltage Vin (FIG. 2). The height of the square wave is equal to the output voltage Vo in a boost converter, which is equal to Vin/l-D.
A typical switching regulator circuit, examples of which are described in the previous sections, regulates the output voltage Vo by modulating the widths of the pulses (duty cycle) on the switching node. This method is usually referred to as pulse width modulation (PWM). The voltage on the switching node changes from 0 to Vin, and Vin to 0, in case of a buck switching regulator, and from 0 to Vo, and Vo to 0, in case of a boost switching regulator, in a short period of time (typically within a few nano-seconds).
The following is an example of a specific aspect in the prior art that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon. By way of educational background, another aspect of the prior art generally useful to be aware of is that it is well known that, in addition to the buck and boost switching regulator circuit topologies described in the previous sections, various other switching regulator circuit topologies exist in the art and include, by way of example and without limitation, polarity inverting, push-pull, forward converter, half-bridge, full-bridge, flyback, CUK, SEPIC, synchronous, asynchronous, isolated and non-isolated topologies, which may be operating in continuous mode, discontinuous mode, interleaved mode, current mode, voltage mode, voltage fed mode, current fed mode or other modes or combinations thereof as is known in the art.
The following is an example of a specific aspect in the prior art that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon. By way of educational background, another aspect of the prior art generally useful to be aware of is that it is well known, and described by Faraday's law, that a time varying electromagnetic field induces a counter electromagnetic field which cancels out the original electromagnetic field. The counter electromagnetic field energy is induced and released as electromagnetic noise into the conductor or radiated into the space in the vicinity of the switching node. The electromagnetic energy, or noise, that travels through a conductor is called conducted noise, and the electromagnetic energy or noise that travels through space is called radiated noise. Often these two are differentiated by their frequency bands.
This conducted and radiated electromagnetic noise is often referred to as electromagnetic interference (EMI) and EMI may interfere with operation of electronic devices. EMI may obstruct, interrupt, or degrade the performance of memory devices, CPUs, and application specific integrated circuits (ASIC)'s, for example, on a computing processor board. EMI may also cause audio circuit degradation. Listeners of audio devices may hear audible EMI noise induced by switching regulators used within the audio devices.
Although switching regulators are known to cause EMI, they are frequently used in electronic devices because of their high power conversion efficiencies, low power losses and compact size.
The following is an example of a specific aspect in the prior art that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon. By way of educational background, another aspect of the prior art generally useful to be aware of is that circuit designer's methods and solutions of addressing switching regulator EMI have typically been passive methods such as installing electrical component filters in noise-susceptible areas or mechanically shielding switching regulators or noise-susceptible electrical devices with metallic nets. Both passive component EMI filtering and metallic net EMI shielding may require bulky and/or costly electrical and mechanical components to be added to a typical electrical device.
In view of the foregoing, it is clear that these traditional techniques are not perfect and leave room for more optimal approaches.
Unless otherwise indicated illustrations in the figures are not necessarily drawn to scale.